Diggy, like Replit or Glitch, is a computational environment.
Diggy can run pretty much any programming language in a protected environment. Of course, as long as there is a binary that runs on Linux.
Your code is executed in a sandboxed environment, and the results are sent back to the browser. Since everything runs in a protected sandbox you cannot access network interfaces or (hopefully!) break anything. See limitations for more detail.
Running CPython 3.9.5
Running Ruby 3.0.0-preview1